The present invention relates to wireless communications in general and, in particular, to certain quality of service enhancements.
Bi-directional wireless systems (such as satellite) may benefit from the use of adaptive coding and modulation (“ACM”). Using ACM, the modulation format and Forward Error Correction (“FEC”) codes for a signal may be adapted to better match the link conditions for each user in a multi-user system. A return channel or other means may be used to report the conditions of a receiving terminal. These link conditions are often characterized by the individual user's (or terminal's) signal-to-noise ratio (“SNR”). In a broadcast system, for example, the waveform broadcast to a number of users includes data packets designated only for an individual terminal (or small group of terminals). A message transmitted to a user requires fewer symbols (and thus less time) when a higher order modulation and higher code rate is used. Lower order modulation and lower code rate are more reliable but require more time to transmit the same size message. Using ACM, each packet may be transmitted at an optimized modulation and coding (“modcode”) level given the destination terminal's link conditions.
In optimizing modcode levels for a destination terminal's link conditions, first-in first-out (FIFO) queueing may be used in traditional systems. However, different sets of data may have different quality of service requirements. It may, therefore, be desirable to have novel techniques for providing certain sets of data with forwarding preferences, while still implementing efficient traffic shaping and allocation using adaptive coding and modulation.